Many countries throughout the world have a vital need for obtaining fresh water from sea water. Typically, island-countries require either the distillation of sea water or the importation of fresh water in order to supply their needs. In many parts of the United States, there are critical water shortages that could be quickly remedied through the distillation of adjacent sea water. However, it has seldom been thought to be cost effective to distill sea water through presently available techniques. As a result, water importation into areas of need has been the typical solution for providing fresh water.
There are many areas of the world that have been relying on the use of oil or natural gas to obtain fresh water. For example, in the U.S. Virgin Islands, about half of the fresh water supply is produced through oil-fired stills. The other half of their fresh water supply is barged from Puerto Rico. These methods of obtaining fresh water are incredibly expensive.
Under presently available techniques, it is possible to distill sea water through application of wave energy. However, under such techniques, the wave energy is used to generate electricity which is, in turn, used to provide heat to the still. (See, for reference, U.S. Pat. No. 4,077,213 issued on Mar. 7, 1978, to Glenn E. Hagen and U.S. Pat. No. Re. 31,111 of Dec. 28, 1982, issued to Glenn E. Hagen.) However, such electrical equipment is expensive, both in initial and maintenance costs.
Another concept would be to skip the electrical step and use the motion of floats on the surface of the sea to pump water vapor in a pressure-difference still. The temperature of the ocean's surface in the area of the Virgin Islands is about 33 degrees C. At that temperature, water will boil if subjected to a vacuum of about 30 millimeters absolute. This suggests that wave-powered cylinders could be used to create a 30 millimeter vacuum and allow the sea water to boil from the heat of the ocean. Unfortunately, steam at this low pressure is not very dense. It would take enormous cylinders to distill a practical amount of fresh water. This arrangement would be both economically and physically impractical.
It is an object of the present invention to provide a system for distilling sea water and other impure aqueous solutions through the use of wave energy.
It is another object of the present invention to provide a scheme for distilling sea water at relatively high temperatures and pressures without generating or needing electricity.
It is still another object of the present invention to provide a sea water distillation apparatus and method that is economically competitive with oil-fired stills.
It is a further object of the present invention to provide a technique for extracting wave energy which maximizes the vacuum imparted to the system per passing wave.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.